kgg

For sewing the 12mm or so of leather as previously stated you need a Class 441 machine like the Juki TSC-441 or clone. Finding Tippmann, Cobra machines on that side of the pond will probably be a chore. Since you are in the UK: For New: I would contact Franklin Co. for Cowboy machines https://www.franklinco.co.uk/about/ For Used: I would contact places like https://leathermachinery.co.uk/ as they seem to have a selection of used machines. Another option would be to import a 441 class clone machine directly from China for probably about the same price as a good used machine would cost in the UK. kgg

Other sources are Temu and Aliexpress. Depending on the quality and quantity find the item on say Temu and then go to Alibaba. Then you could buy one off say Temu and chances are the manufacturer will have their label on the item then contact that manufacturer directly. Sewing thread: A&E (made in Canada) http://www.amefird.ca/home/ General Items like rivets and Class 441 needles https://aaronmartin.com/ General Sewing Items like needles/zippers/binding for upholstery class machines https://www.wawak.ca/ General Sewing Items like Fieblings Dye, hand sewing thread and needles, hardware https://lonsdaleleather.com . It is cheaper for me to purchase dye from them and pay the shipping then buy it anywhere in Ontario. I'm in Eastern Ontario have purchased most of my leather in Montreal but have purchase on occasion purchased from Zelikrovitz in Ottawa https://www.zelistore.com/en-ca?srsltid=AfmBOooyTM4vv_4UX6qKoAuFBz284O3uiStWwlYvo3ns8cR66VQuM-Jv To narrow your search what kind of items are you looking for???? kgg

I use single action airbrushes as I just couldn't get the hang of the double action airbrushes, like the Timbertech Airbrush Kit and the Paasche Airbrush that are siphon feed rather then gravity feed with the braided nylon hoses. I would push the pressure probably up to 40 - 45 lbs from my normal of 30lbs. You may have to: i) use a real compressor rather then an airbrush compressor just for the volume of air that maybe required. ii) detail spray gun like the Titan Tools Siphon Feed Detail Spray Gun if the consistency in doing the large pieces isn't what you need and to reduce the number of dye bottle changes. The airbrushes that I have can realistically hold about 20ml while the detail spray gun could probably hold close to 200ml. I have done 2' x 2' pieces of leather using my airbrushes with the airbrush compressor for both oiling (JOJOBA oil) and dying. I would definitely try the inexpensive Timbertech airbrush first, practice on a piece of cardboard of the same size first to get your spray and your rhyme right. This topic on my setup may help.

Before attempting to removing the bobbin assembly I would remove the bottom cover on the cylinder arm as you have a 50/50 chance that the tip of the needle fell down there. kgg

Yup. Also another point is how the ink will react with leather that has been oiled etc and the longevity of the ink. The old inks could last twenty plus years with detail and colors still there. Today I see a lot of tattooing that needs to be refreshed after 3 or 4 years. kgg

My two cents worth in addition to @Wizcrafts comments: Neither. They are upholstery class machines with a rated thread size max of V138 as a top and in the bobbin and typically a max sewing thickness of 3/8". That said depending on how thick you are planning on sewing sometimes you can use v207 in both the bobbin and as a top thread with thinner /softer leather more times you will be able to use v207 as a top thread and v138 in the bobbin. The drawback with using different thread sizes, top vs bobbin, is the strength of the seam will be only as good as the smallest thread size. As a note the brand name machines rated their machines on the thread size it could sew in the max thickness not what size of thread you could stuff through the eye of the needle. All the machines you have listed are rated for a #24 needle which is good for V207 in thinner stuff and V138 in thicker. Doing the conversion to the larger "U" size bobbin is not a simple pop-off and drop-in process which will in reality only get you more bobbin thread. The conversion is not going to get above V207 (limited by needle size) and depending on how thick / tough the leather is you still maybe limited to V138 as the top thread as well as in the bobbin. Is it worth the effort?? I don't know. If you need to sew V207 and above in thick or tough leather consistently these machines are the probably the wrong class of machine. You maybe able to trick the machine by increasing the torque using a speed reducer but chances are over the long haul you are going to damage the internals components of the machine. The term you used "extremely heavy" for thread is a relative thing. Domestic sewers consider V69 to be heavy duty while upholstery class machine users consider V207 to be heavy duty while those using saddle/ holster capable machines consider V415 as heavy duty and then you get into threads that hand sewers use which would be above V415. What is the thickness of leather you want to sew????? kgg

Airbrushing for both the dye and oiling. kgg

The main difference is a clutch motor is running at full rpm's (1450 or 1750) as soon as you turn the power on and like a manual transmission in a vehicle you ease the on clutch. The servo motors don't spin until you depress the "go" pedal. All servo motors have a "startup jump" with the brushless typically having a more noticeable "jump" then the brushed servo motors. You can reduce this somewhat by reducing the pulley on the servo motor, installing a speed reducer and buying a better quality servo motor. Typically the more internal coils the servo motor has the less "jump" experienced but check the startup rating of the servo motor a lot of the cheaper ones have a 500 rpm rating. kgg

I would reconsider by the time you change the clutch motor out for a servo barring anything else you are up to about $1100 for a machine that came to the market in 1976. If you need parts they are going to be either hard to fine or expensive. Since you mentioned the Consew 226 which came to the market around 1960 I would go more for a newer Consew 206RB-5 which has a larger bobbin and costs about $1800 new. kgg

My 2 cents worth: Problem 1: Yes I agree oiling first will change the color of the leather however you are going to dye it anyway. The upside to dying first is the dye will penetrate deeper in the leather and allow the dye to go deeper as well. Problem 2: If you convert to airbrushing for both the oiling and dying you will, depending on the size of the piece, get a more even streak free dye covering. Also you will use less oil and less dye in the process. Which method of how you are applying the oil and dye to the leather?? Rag, sponge, brush etc.. kgg

The .3mm thickness is really thin leather. The .3mm would sort equate to about 3/4 oz in leather which is about the thickness of three sheets of regular copier paper. I suspect the problem is mainly do to the leather thickness. With such thin leather it will lend itself to stretching which will throw consistent stitch lengths off and the leather probably is being sucked / forced down ever so slightly into the needle hole of the feed dog as well as along the outside edges of the feed dog in the space between the feed dog and the needle plate opening. I have seen this type of problem with my Juki DNU-1541S when I am sewing thin flexible items as it has a large needle opening in the feed dog and just loves to suck things down that hole. I have used regular weight copier paper placed on the feed dog side of the items with some success in the past. A couple of questions. Which domestic machine are you using, what thread size are you using and what size of needle? kgg

Interesting discussion. I do think it would be an interesting project and would be interested on how it turns out for your application. I'm with @dikman I don't use the needle positioner on the brushless servo motors since I sew slow. I like to keep my setups as simple as possible, brushed servo motor maybe a speed reducer and machine. I do have a couple of machines with the brushless NP compliant brushless servo motor without the NP installed but In reality I can't wait for those to throw in the towel or even a blown fuse so I can justify replacing them with a brushed servo motors. kgg

I don't hand sew but I would think maybe leather gloves something similar to those used for Cycling, Weight Lifting or Wheelchair use would work. kgg

Yes and No. The manuals do show how to wind a bobbin, load/unload a bobbin, what direction the bobbin should turn when the bobbin thread is pulled and what screw to adjust for increasing or decreasing the tension just not how not how to get the tension close to what is needed for a given thread size or what not to do when adjusting the tension screw. Note: 1) Juki LS-1341 can have it's bobbin tension adjust while in your hand and not in the machine and you can do a drop test like a flatbed machine since it is a split case setup. 2) The manuals indicate the bobbin should turn clockwise NOT counter clockwise. Here are three examples from the Juki manuals. Other Brand Name and Clone machines may differ. : i) Juki LS-1341 (compound walking foot cylinder bed)--> threading a bobbin ii) Juki LS-1341 (compound walking foot cylinder bed) --> adjusting bobbin tension iii) Juki DNU-1541S (compound walking foot flatbed)--> threading a bobbin iv) Juki DNU-1541S (compound walking foot flatbed) --> adjusting bobbin tension v) Juki DU-1181N (walking foot flatbed) --> threading a bobbin vi) Juki DU-1181N (walking foot flatbed) --> adjusting bobbin tension kgg

The bobbin is the same it's the bobbin case that is different. Here is a good video on doing a drop test on a flatbed machine. The same applies for a Juki compliant bobbin case on a cylinder arm. kgg

This a typical location for the "tilt stump". Typically just made of plastic, pressure fitted into a hole drilled into the table top and meant as a temporary rest. The machine " slithered off the table hinge and into the drip pan " indicates to me incorrect / damaged hinge and or hinge installation. I have never had a head slip off and with my stubby fingers I am also titling my flatbed machines back to install / remove bobbins. kgg

Downside I think is getting the bobbin tension adjusted. The Juki style is where the bobbin is placed in the top half part of the bobbin assembly, threaded and tension adjusted while still in your hand and then dropped in place. Personally I like being able to adjust the bobbin tension this way as I can do a bobbin tension drop test. kgg

That is correct for the Cobra Class 26 it does not have a Juki compliant bobbin assembly. Here is a video for the bobbin installation. kgg

My two cents worth: Notes i) The recommended size of needle for Tex135 (V138) is a 140 (#22) thin material, 160 (#23) medium material and 180 (#24) thick material. ii) Your 130 needle is really meant for Tex90 (V92). A good reference chart is ( https://www.tolindsewmach.com/thread-chart.html ). iii) V45 has a breaking strength of 7.5 lbs iv) V69 has a breaking strength of 11 lbs v) V92 has a breaking strength of 14.5 lbs vi) V138 has a breaking strength of 22 lbs If I'm not mistaken the 269 is cylinder arm and by adding a simple table top attachment you would have sorta kinda a flatbed for versatility. Personally I wouldn't bother changing the thread size and do all the sewing with Tex135 (V138). kgg

Yes, I have purchased bobbins and bobbin cases for a Sailrite clone. I purchased them from CKPSMS brand and they were decent quality. I have also bought from Aliexpress. kgg

I guess "reasonably priced" is a relative thing. Each needle at $28.57 AUD ($26.23 CAD) and I thought paying $4.50 CAD for 794S size 250 was expensive. kgg

The simple answer is it will not be suitable for leather work. This is a drop feed machine made for sewing fabric at high speeds. kgg

I'm glad you had good success with the dealer. Seems strange, you should contact them or Alder directly for a solution. Ah, you should bought a Juki. kgg

My take: i) Lower startup speed is determined by the amount of bottom end torque it was designed for and how good the electronic closed speed loop controller. Even if you can change the startup parameter to something less then 500 rpm the motor you will introduce some annoying things like stalling, surges and poorer rpm regulation. ii) The cheaper servo motors have 6 internal coils while the better ones have 12 coils which will typically provide better lower startup speed that is more consistent and smoother not just because of the added coils but chances are of they will have better electronic controls. I could not find any information on that particular servo motor but it would be a safer bet to assume it has 6 internal coils or call / email the manufacturer. iii) The only way of getting a reliable slower, smoother startup speed with the brushless servo motors is to install a speed reducer or buy a better servo motor. Getting the 1 stitch per second is probably equal to about 60 RPM. This I think is a bit unrealistic. If you really need that low a speed you would have to build an 8.33 to 1 speed reducer and probably change the servo motors shaft pulley. Keep in mind that an off the shelf speed reducer is 3 to 1 which will give you about 166 rpm. iv) to properly determine a realistic sewing speed you would need to do a pulley calculation knowing the size of the sewing machines handwheel and the size of the servo motors pulley based on the minimum startup speed. kgg

This wouldn't have been my first choice of a machine mainly due to the hole it would punch through the material, 2.5mm diameter unless you are sewing items above 1/2"(12.5mm) in thickness or saddles. I would have probably gone with a Juki LS-1341 or clone with a speed reducer as it would use a smaller diameter needle the system 135 x 16 x needle size for leather. My understanding is the 969 is a class 441 machine that takes the system 7x 3, 794 or 1000 needles (Schmetz). There are needles available for 7x3 or 794 from #19-#27 (120-220) for V92 to V415 thread. I would talk to the dealer to track down the needles if you are going to keep the machine and maybe discuss exchanging the machine for something like a 869 which would take the system 135 x 16 needles . kgg